This chapter investigates an unmanned aerial vehicle (UAV)-enabled nonlinear wireless power transfer (WPT) network which involve multiple ground sensor nodes (SNs). The UAV performs as an energy source to transfer energy wirelessly to these SNs. For efficiently energy harvesting (EH), the UAV is equipped with a three dimensional (3D) uniform linear array (ULA) antenna, facilitating analog beamforming for focused power transfer. Given the UAV energy consumption and adopting a practical nonlinear EH model, we delve into the UAV energy efficiency maximization for WPT operation which leads to the formulation of an efficiency maximization problem through jointly designing analog beamforming, UAV trajectory planning, and transmit power allocation. To tackle the intricate non-convex optimization challenge, we introduce a cosine-based approximation for the complicated 3D ULA antenna pattern which holds certain convexity. Synergizing the convexity of the modified antenna pattern with that of the nonlinear EH model, we construct a convex subproblem centered on given local point where solving this subproblem iteratively ensures a gradual enhancement in the objective. Simulation results confirm the algorithm convergence and performance benefits.